DNA sequencing is the process of reading the nucleotide bases in a DNA molecule. It includes any method or technology that is used to determine the order of the four bases—adenine, guanine, cytosine, and thymine—in a strand of DNA.
Knowledge of DNA sequences is useful for basic biological research, and in numerous applied fields such as diagnostic, biotechnology, forensic biology, and biological systematics. The advent of DNA sequencing has accelerated biological research and discovery. The rapid speed of sequencing attained with modern DNA sequencing technology has been instrumental in the sequencing of the human genome, in the Human Genome Project. Related projects, often by scientific collaboration across continents, have generated the complete DNA sequences of many animal, plant, and microbial genomes.
New development in the medical field (e.g., personalized medicine) and basic biological research (e.g., animal or plant genome projects) calls for rapid sequencing of large number (e.g., above 10,000) of DNA fragments in a practical period of time (e.g., several hours to several days), which is usually referred to as a high-throughput sequencing. Traditional chemistry-based and optic-based DNA sequencing methods such as the Maxam-Gilbert method and Chain-termination methods suffer from their requirements of complex sample preparation and slow rate of base detection, and are generally unsuitable in these applications.
Exemplar high-throughput sequencing techniques include Massively Parallel Signature Sequencing (MPSS) developed by Lynx Therapeutics, Polony sequencing developed by Prof. George Church at Harvard University, parallelized pyrosequencing developed by 454 Life Sciences (now Roche Diagnostics), SOLiD sequencing developed by Applied Biosystems (now Life Technologies), pH-based semiconductor sequencing developed by Ion Torrent (now Life Technologies), nanopore sequencing, etc.